1. Technical Field
The present invention relates to a printer and to a control method for the printer.
2. Related Art
Roll paper printers such as receipt printers and coupon printers that print images while conveying a print medium from a roll through a media transportation path are known from the literature. Printers of this type index the roll paper from the roll to the printing start position by means of a paper transportation mechanism including paper transportation rollers, and then print an image according to the print data while advancing the roll paper at a predetermined speed.
If the roll paper runs out while working, this type of receipt printer or coupon printer cannot correctly print the print data to be printed, the queue of receipts or coupons to be printed continues to grow, and work cannot proceed efficiently. The paper also curls tightly toward the inside diameter end of the roll, and the paper cannot be smoothly discharged at the very end of the roll due to the tight paper curls. Curled receipts and coupons are also unsightly and difficult to use.
To avoid such problems Japanese Unexamined Patent Appl. Pub. JP-A-H06-115787 teaches a printer that has a strain gauge in the bottom of the roll paper holder and displays how much roll paper remains in three stages according to the strain that is indicated by the strain gauge according to how much roll paper remains in order to keep the user informed of how much roll paper remains.
Japanese Unexamined Patent Appl. Pub. JP-A-2004-223715 teaches a printer that applies tension, which is determined, by how much roll paper remains, in the opposite direction as the direction in which the roll paper curls in order to remove the unwanted curling.
Various printers that execute particular operations depending on the remaining amount of roll paper are thus known from the literature. However, while tension can be applied to remove curling as described in Japanese Unexamined Patent Appl. Pub. JP-A-2004-223715, when there is very little roll paper remaining and the trailing end of the roll paper separates from the core, tension cannot be applied to the roll paper because the trailing end is free. As a result it may not be possible to remove curling near the trailing end of the roll paper.
As shown in FIG. 7 and FIG. 8, inkjet printers that print to roll paper by discharging ink from the nozzles of a print head typically have two transportation rollers 71 and 72 disposed on opposite sides of the path of the carriage 74 on which the print head is mounted. This printer stops paper transportation when the trailing end 76 of the roll paper is detected and moves the carriage to a standby position in order to cap the print head to prevent the ink in the nozzles of the print head mounted on the carriage 74 from drying out. If paper transportation is stopped immediately when the trailing end 76 of the roll paper is detected, the carriage 74 moves to the standby position while the trailing end 76 of the roll paper remains between the two transportation rollers 71 and 72 and is thus in the path of the carriage.
More specifically, when the roll paper 75 is loaded so that the paper unrolls in the counterclockwise direction (the direction of arrow x) as shown in FIG. 7A, the trailing end 76 of the roll paper dangles freely as shown in FIG. 7B.
When the roll paper 75 is loaded so that the paper unrolls in the clockwise direction (the direction of arrow y) as shown in FIG. 8A, the trailing end 76 of the roll paper may spring back as shown in FIG. 8B.
In both of the situations shown in FIG. 7B and FIG. 8B, however, the roll paper 75 is left to interfere with moving the carriage 74 to the standby position. In some cases this can cause a paper jam and printer malfunction. Furthermore, the ink meniscus in the nozzles can also be broken and consistent print quality cannot be maintained if the paper contacts the print head.
Furthermore, when the paper detector 73 detects the trailing end 76 of the roll paper 75 and the user installs a new roll of paper, it is preferable to remove the small amount of roll paper left in the transportation path to avoid a paper jam.